U.S. patent application number 12/022416 was filed with the patent office on 2008-08-21 for dehydrogenation catalyst, process for preparation, and a method of use thereof.
Invention is credited to Ruth Mary KOWALESKI.
Application Number | 20080200741 12/022416 |
Document ID | / |
Family ID | 39283228 |
Filed Date | 2008-08-21 |
United States Patent
Application |
20080200741 |
Kind Code |
A1 |
KOWALESKI; Ruth Mary |
August 21, 2008 |
DEHYDROGENATION CATALYST, PROCESS FOR PREPARATION, AND A METHOD OF
USE THEREOF
Abstract
A process for preparing a dehydrogenation catalyst comprising
preparing a mixture comprising a treated regenerator iron oxide and
at least one additional catalyst component; and calcining the
mixture wherein the treated regenerator iron oxide is prepared by
washing a regenerator iron oxide at a temperature below 350.degree.
C. such that the treated regenerator iron oxide has a chloride
content of at most 500 ppmw relative to the weight of iron oxide,
calculated as Fe.sub.2O.sub.3; the catalyst prepared by this
process and the use of the catalyst in a dehydrogenation
process.
Inventors: |
KOWALESKI; Ruth Mary;
(Cypress, TX) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
39283228 |
Appl. No.: |
12/022416 |
Filed: |
January 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60887185 |
Jan 30, 2007 |
|
|
|
Current U.S.
Class: |
585/444 ;
502/304; 502/316; 502/328; 502/338 |
Current CPC
Class: |
B01J 23/8872 20130101;
B01J 37/0009 20130101; B01J 35/0026 20130101; B01J 23/78 20130101;
B01J 23/83 20130101; C07C 2523/02 20130101; C01P 2006/80 20130101;
C01P 2004/64 20130101; C01G 49/06 20130101; B01J 35/1009 20130101;
C07C 2523/04 20130101; B82Y 30/00 20130101; C01P 2002/52 20130101;
C07C 2523/83 20130101; C01G 49/009 20130101; C01P 2006/16 20130101;
C07C 2523/881 20130101; B01J 23/745 20130101; B01J 37/06 20130101;
C07C 15/46 20130101; C01P 2006/12 20130101; C07C 5/3332 20130101;
C01P 2006/14 20130101; C07C 5/3332 20130101 |
Class at
Publication: |
585/444 ;
502/304; 502/316; 502/328; 502/338 |
International
Class: |
C07C 2/64 20060101
C07C002/64; B01J 23/745 20060101 B01J023/745; B01J 23/83 20060101
B01J023/83; B01J 23/78 20060101 B01J023/78; B01J 23/888 20060101
B01J023/888; B01J 23/88 20060101 B01J023/88 |
Claims
1. A process for preparing a dehydrogenation catalyst comprising
preparing a mixture comprising a treated regenerator iron oxide and
at least one additional catalyst component; and calcining the
mixture wherein the treated regenerator iron oxide is prepared by
washing a regenerator iron oxide at a temperature below 350.degree.
C. such that the treated regenerator iron oxide has a chloride
content of at most 500 ppmw relative to the weight of iron oxide,
calculated as Fe.sub.2O.sub.3.
2. A process as claimed in claim 1 wherein the regenerator iron
oxide prior to washing has a chloride content of at least 700 ppmw
relative to the weight of iron oxide, calculated as
Fe.sub.2O.sub.3.
3. A process as claimed in claim 1 or claim 2 wherein the treated
regenerator iron oxide has a chloride content of at most 300 ppmw
relative to the weight of iron oxide, calculated as
Fe.sub.2O.sub.3.
4. A process as claimed in any of claims 1-3 wherein the treated
regenerator iron oxide is prepared by washing the regenerator iron
oxide with water.
5. A process as claimed in any of claims 1-4 wherein the treated
regenerator iron oxide is prepared by washing the regenerator iron
oxide with an acidic solution.
5. A process as claimed in claim 5 wherein the acidic solution is
selected from the group consisting of acetic acid, formic acid and
citric acid.
7. A process as claimed in claim 4 wherein the process comprises
contacting the regenerator iron oxide with water to form a slurry,
contacting the slurry with an aqueous solution having a pH higher
than the pH of the slurry, drying the slurry and washing the dried
slurry with water.
8. A process as claimed in claim 7 wherein the slurry is heated to
a temperature of at most 200.degree. C.
9. A process as claimed in any of claims 1-8 wherein the additional
catalyst component comprises a metal selected from the group
consisting of calcium, magnesium, molybdenum, tungsten, cerium, and
combinations thereof.
10. A process as claimed in any of claims 1-8 wherein potassium or
a compound thereof is added to the treated regenerator iron oxide
mixture.
11. A process as claimed in any of claims 1-10 wherein the mixture
is calcined at a temperature of from about 600.degree. C. to about
1300.degree. C.
12. A catalyst produced by the process of any of claims 1-11
wherein the dehydrogenation catalyst comprises from 10 to 95 weight
percent iron oxide relative to the total weight of the
dehydrogenation catalyst, calculated as Fe.sub.2O.sub.3, and from 5
to 40 weight percent potassium, calculated as K.sub.2O.
13. A catalyst as claimed in claim 12 wherein the dehydrogenation
catalyst further comprises from 1 to 25 weight percent cerium,
calculated as CeO.sub.2.
14. A dehydrogenation process, comprising: providing a reactor
loaded with a catalyst as claimed in claim 12 or claim 13,
introducing a feedstock into the reactor, and operating the reactor
under conditions suitable to yield a dehydrogenation product.
15. A method of improving the operation of a dehydrogenation
system, including a dehydrogenation reactor that is loaded with a
non-regenerator iron oxide based dehydrogenation catalyst, wherein
said method comprises: removing from said dehydrogenation reactor
said non-regenerator iron oxide based dehydrogenation catalyst;
replacing the thus-removed non-regenerator iron oxide based
dehydrogenation catalyst with a regenerator iron oxide based
dehydrogenation catalyst as claimed in claim 12 or claim 13 to
thereby provide a modified dehydrogenation system; and operating
said modified dehydrogenation system under dehydrogenation process
conditions.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/887,185, filed Jan. 30, 2007, which is hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to a dehydrogenation catalyst derived
from a regenerator iron oxide, the preparation thereof and its use
in a dehydrogenation process.
BACKGROUND OF THE INVENTION
[0003] In the field of catalytic dehydrogenation of hydrocarbons
there are ongoing efforts to develop improved catalysts that may be
made at lower costs. One way of reducing the cost of iron oxide
based dehydrogenation catalysts is to use lower cost raw materials.
One such low cost raw material is regenerator iron oxide produced
from hydrochloric acid waste liquid generated from steel pickling.
The use of regenerator iron oxide as the iron oxide component of an
iron oxide based dehydrogenation catalyst may provide significant
cost savings in raw material costs in comparison to the use of
other more conventional commercial iron oxides.
[0004] The use of regenerator iron oxide as a catalyst component is
described in U.S. Pat. No. 5,401,485, which discloses catalysts
containing iron oxide obtained by the spray roasting of a
hydrochloric acid solution containing iron chloride. A significant
disadvantage associated with the use of regenerator iron oxide as a
catalyst component is that the resulting catalysts may have what is
considered herein to be high levels of residual chloride that
results in less effective dehydrogenation catalysts. The '485
patent discloses the use of sulfuric acid to reduce the residual
chloride level in iron oxides.
[0005] The prior art also describes processes for providing a
regenerator iron oxide that has a reduced chloride content, for
example U.S. Patent Application Publication 2004/0097768 and U.S.
Pat. No. 6,863,877. The processes described in both of these
documents require a costly high temperature heat treatment step
that has negative effects on the regenerator iron oxide being
treated, such as reducing the surface area of the iron oxide.
[0006] Accordingly, it would be an advancement in the art to
provide a dehydrogenation catalyst and process for forming the
catalyst that uses low cost materials but provides a catalyst with
a high initial activity.
SUMMARY OF THE INVENTION
[0007] The invention provides a process for preparing a
dehydrogenation catalyst comprising preparing a mixture comprising
a treated regenerator iron oxide and at least one additional
catalyst component; and calcining the mixture wherein the treated
regenerator iron oxide is prepared by washing a regenerator iron
oxide at a temperature below 350.degree. C. such that the treated
regenerator iron oxide has a chloride content of at most 500 ppmw
relative to the weight of iron oxide, calculated as
Fe.sub.2O.sub.3.
[0008] The invention provides a catalyst comprising treated
regenerator iron oxide wherein the dehydrogenation catalyst
comprises from 10 to 95 weight percent iron oxide relative to the
total weight of the dehydrogenation catalyst, and calculated as
Fe.sub.2O.sub.3, and from 5 to 40 weight percent potassium,
calculated as K.sub.2O.
[0009] The invention further provides a dehydrogenation process,
comprising: providing a reactor loaded with a catalyst comprising
treated regenerator iron oxide, introducing a feedstock into the
reactor, and operating the reactor under conditions suitable to
yield a dehydrogenation product.
[0010] The invention further provides a method of improving the
operation of a dehydrogenation system, including a dehydrogenation
reactor that is loaded with a non-regenerator iron oxide based
dehydrogenation catalyst, and wherein said method comprises:
removing from said dehydrogenation reactor said non-regenerator
iron oxide based dehydrogenation catalyst; replacing the
thus-removed non-regenerator iron oxide based dehydrogenation
catalyst with a regenerator iron oxide based dehydrogenation
catalyst comprising treated regenerator iron oxide to thereby
provide a modified dehydrogenation system, including said
dehydrogenation reactor that is loaded with said regenerator iron
oxide based dehydrogenation catalyst; and operating said modified
dehydrogenation system under dehydrogenation process
conditions.
DETAILED DESCRIPTION OF DRAWINGS
[0011] FIG. 1 presents comparative plots showing the calculated
activity (T70) of tested catalysts as a function of time in days of
use.
[0012] FIG. 2 presents comparative plots showing the actual
conversion of ethylbenzene provided by tested catalysts as a
function of time in days of use.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present invention provides a catalyst that satisfies the
need for lower cost iron oxide based catalysts. The use of a
treating step at a temperature below 350.degree. C. provides a
regenerator iron oxide with a reduced chloride content and physical
characteristics that are suitable for producing effective
dehydrogenation catalysts. The surface area of the regenerator iron
oxide provides more active sites for incorporation of additional
catalyst components than other regenerator iron oxides that have
been treated by high temperature heat treatments. The catalyst
produced by the inventive method demonstrates a higher initial
activity than other regenerator iron oxide based dehydrogenation
catalysts that have not undergone a similar treating step to
sufficiently reduce the residual chloride content.
[0014] The regenerator iron oxide component of the catalyst is an
iron oxide derived from waste pickle liquor, an aqueous solution of
hydrochloric acid and iron chloride waste liquid generated from
steel pickling. This regenerator iron oxide, in general, may be
made by the heat decomposition of iron chloride (either iron
dichloride, or iron trichloride, or both) preferably in an
oxidizing atmosphere, to yield iron oxide. More specifically, the
regenerator iron oxide is made by spray roasting of waste pickle
liquor by any method known to those skilled in the art, for example
the Ruthner process described in U.S. Pat. No. 5,911,967.
[0015] The spray roasting may be conducted by spraying the waste
pickle liquor into a roaster where it is exposed to a heated source
of oxygen, for example air, and where the iron chloride, for
example, FeCl.sub.2 and/or FeCl.sub.3, undergoes a thermal
conversion to form iron oxide that is predominantly in the form of
hematite (Fe.sub.2O.sub.3). The spray roasting may occur at spray
roasting temperatures exceeding 300.degree. C. and ranging upwardly
to 800.degree. C. or even higher temperatures. The iron oxide is
recovered as regenerator iron oxide.
[0016] The regenerator iron oxide generally has an appreciable
level of residual chloride content. The residual chloride content
of such regenerator iron oxide is typically in the range of from
about 700 ppmw to 20,000 ppmw, but more typically, the residual
chloride concentration is in the range of from 800 ppmw to 10,000
ppmw. Thus the chloride concentration of the regenerator iron oxide
may be greater than 1000 ppmw.
[0017] Methods of reducing the chloride concentration in the
regenerator iron oxide have been discussed in the prior art, but
each of these methods has disadvantages when the regenerator iron
oxide is intended for use as a component in a dehydrogenation
catalyst.
[0018] According to the present invention, the regenerator iron
oxide is not calcined to remove chloride as taught by some of the
prior art methods because this causes undesirable negative effects
on the iron oxide structure. For example, calcining the regenerator
iron oxide results in an iron oxide with a decreased surface area
that can inhibit effective incorporation of additional catalyst
components in the catalyst manufacturing process.
[0019] The regenerator iron oxide is treated by washing at a
temperature below 350.degree. C. to reduce the chloride content of
the iron oxide. The treatment of the regenerator iron oxide may
comprise acid washing, but preferably comprises water washing under
suitable conditions to reduce the chloride content.
[0020] In one embodiment, the regenerator iron oxide is washed with
an acid to reduce the chloride content. Acids suitable for use in
the acid treatment of the regenerator iron oxide may include those
acids that are decomposable to volatile compounds under the
conditions of the catalyst preparation as described herein and can
include organic acids and inorganic acids including those acids
noted in U.S. Pat. No. 5,401,485 and U.S. Pat. No. 6,863,877, which
are both incorporated herein by reference. Examples of organic
acids include carboxylic acids such as formic acid, acetic acid and
citric acid. Preferred organic acids include acetic acid and citric
acid. Possible inorganic acids include carbonic acid, nitric acid,
nitrous acid, phosphoric acid, phosphorous acid, sulfuric acid, and
sulfurous acid. Among these acids, the preferred inorganic acids
include nitric acid, nitrous acid, sulfuric acid, and sulfurous
acid. The inorganic acids used in the acid treatment of the
regenerator iron oxide are preferably in an aqueous solution having
a Normality (equivalents of solute per liter of solution) in the
range of from 0.01 to 4, preferably, from 0.05 to 3, and, most
preferably, from 0.1 to 2.
[0021] In a preferred embodiment, the regenerator iron oxide is
washed with water. The regenerator iron oxide may be simply washed
with water to reduce the chloride content, but it is preferred to
carry out certain steps prior to the water washing. It is preferred
to prepare a slurry by contacting the regenerator iron oxide with
water. The slurry may contain 5-25% solids by weight, although the
percent of solids may be higher or lower. The addition of water to
a regenerator iron oxide typically produces an acidic slurry, and
the acidic nature of the slurry can make the remaining steps more
difficult. It is preferred therefore to raise the pH of the slurry
to make it easier to handle. The pH of the slurry is generally
adjusted by adding a solution with a pH that is greater than the pH
of the slurry solution. The solution that is added may be an
aqueous solution comprising one or more of the following: sodium
hydroxide, potassium hydroxide, calcium hydroxide, sodium
carbonate, and lime. The slurry is then filtered, washed and dried.
The resulting dried slurry material may undergo any number of
filtering, washing and/or drying cycles. The resulting material may
then be ground or deagglomerated after drying. Other embodiments of
water washing are described in JP 5043252A, and Japanese Laid Open
Patent Application No. 279045.
[0022] The pH adjustment of the slurry is optional, but generally
results in a more efficient filtration step. The pH of the slurry
is preferably increased to a pH of at least 5, and it may be
increased even more, for example to a pH of 7. The pH however may
be raised to any level above the pH of the original slurry.
[0023] The washing times, volumes and number of cycles can be
varied to achieve the desired product properties.
[0024] The filtration may be typically carried out for a period of
time from about 30 minutes to about 10 hours, or more typically
from about 3 hours to about 7 hours. The filtration time may be
determined by the desired moisture content of the filter cake. The
moisture content may typically be in the range of from about 5% to
about 50% residual moisture, or preferably from about 15% to about
40%. The filtration may typically be carried out at a temperature
in the range of from about 0.degree. C. to about 100.degree. C., or
preferably from about 20.degree. C. to about 75.degree. C.
[0025] The washing may be carried out for any amount of time needed
to provide a regenerator iron oxide with a sufficiently reduced
chloride content. The washing time may be divided among more than
one washing cycle. The conductivity of the wash water may be
measured to provide details on the effectiveness of the washing.
For example, the regenerator iron oxide may be washed until the
conductivity of the wash water is below a certain level, for
example, below 100 .mu.S, below 50 .mu.S, or below 25 .mu.S. A
typical washing time may be from about 20 minutes to 20 hours, or
preferably from about 1 hour to 10 hours. The washing may typically
be carried out at a temperature from about 0.degree. C. to about
100.degree. C., or preferably from 20.degree. C. to about
75.degree. C.
[0026] The drying step may typically be carried out at a
temperature ranging from 25.degree. C. to about 350.degree. C., or
preferably from about 100.degree. C. to about 200.degree. C. The
desired moisture content of the treated regenerator iron oxide may
determine the drying time. The desired moisture content may be in
the range of from about 0.1% to about 20% residual moisture,
preferably from about 0.2% to about 5%, more preferably from about
0.2% to about 1%, and most preferably from about 0.2% to about
0.5%.
[0027] The type of filtration and drying equipment used may be any
known to those skilled in the art. The filtration equipment may
include a membrane filter press, a chamber filter press or a tube
press. The drying equipment may be as simple as blowing hot air, or
may include the use of a drying oven or such methods as spin flash
drying.
[0028] The treated regenerator iron oxide may be dried, but the
treated regenerator iron oxide is not calcined. The temperature in
the treating, filtering, washing and drying steps should not exceed
350.degree. C. Preferably, the temperature in these steps should be
at most 300.degree. C., or more preferably at most 200.degree.
C.
[0029] The chloride content of the treated regenerator iron oxide
is at most 500 ppmw, relative to the weight of iron oxide,
calculated as Fe.sub.2O.sub.3. The chloride content is preferably
at most 300 ppmw, or more preferably at most 100 ppmw. The chloride
content of the treated regenerator iron oxide is in the range of
from 1 ppb to 500 ppmw, preferably from 1 ppmw to 300 ppmw, more
preferably from 5 ppmw to 250 ppmw, and most preferably from 10
ppmw to 200 ppmw.
[0030] The treated regenerator iron oxide may have a BET surface
area in the range of from about 2 m.sup.2/g to about 10 m.sup.2/g,
or from about 3 m.sup.2/g to about 7 m.sup.2/g. The surface area of
the treated regenerator iron oxide may be within a range of from
about 50% of the surface area of the untreated regenerator iron
oxide to about 200% of the surface area of the untreated
regenerator iron oxide, or from about 75% to about 150%, or from
about 90% to about 125%. The surface area may be at least 2
m.sup.2/g, at least 2.5 m.sup.2/g, at least 3 m.sup.2/g, or at
least 3.5 m.sup.2/g. As the term is used herein, surface area is
understood to refer to the surface area as determined by the BET
(Brunauer, Emmett and Teller) method as described in the Journal of
the American Chemical Society 60 (1938) pp. 309-316.
[0031] To prepare a catalyst, a mixture is prepared that comprises
the treated regenerator iron oxide, a Column 1 metal or compound
thereof and at least one additional catalyst component. The mixture
may be prepared using any method known to those skilled in the art.
The proportions of the catalyst components that are mixed together
to form the mixture are such as to ultimately provide a
dehydrogenation catalyst having an iron oxide content in the range
of from 10 to 95 weight percent, based on the total weight of the
final catalyst, and is calculated as Fe.sub.2O.sub.3. It is
preferred for the iron oxide content of the catalyst to be in the
range of from 40 to 90 weight percent, and more preferably in the
range of from 60 to 85 weight percent.
[0032] In a preferred embodiment, the treated regenerator iron
oxide is present in the mixture in an amount in the range of from
20 to 100 weight percent of the iron oxide, more preferably in the
range of from 50 to 95 weight percent, and most preferably, from 75
to 92 weight percent, calculated as Fe.sub.2O.sub.3.
[0033] The mixture may also comprise yellow iron oxide. Yellow iron
oxide is a hydrated iron oxide that is frequently depicted as
.alpha.-FeOOH or Fe.sub.2O.sub.3.H.sub.2O. The chloride content of
the yellow iron oxide is preferably less than the chloride content
of the treated regenerator iron oxide. Because sources of yellow
iron oxide are generally those other than iron oxides produced by
heat decomposition of iron chloride, the yellow iron oxide
typically will have a chloride content less than that of the
treated regenerator iron oxide. The chloride content of the yellow
iron oxide is typically at most 500 ppmw, based on the weight of
the yellow iron oxide. The chloride content of the yellow iron
oxide is preferably at most 100 ppmw, and more preferably at most
50 ppmw.
[0034] The amount of yellow iron oxide used in the preparation of
the catalyst mixture may be up to 50 weight percent of the total
weight of the iron oxide. While it may be desirable to not use
yellow iron oxide in the mixture, when yellow iron oxide is used,
it is preferred for the amount of yellow iron oxide to be present
in the mixture in an amount in the range of from 1 to 50 weight
percent. More preferably, the amount of yellow iron oxide in the
catalyst mixture is in the range of from 5 to 30 weight percent,
and most preferably from 8 to 25 weight percent.
[0035] Minor amounts of other iron oxides or iron oxide providing
compounds may be combined with the mixture, but the use of such
other iron oxides or iron oxide providing compounds is generally
not preferred or even desired. Examples of such other iron oxides
include black iron oxide and red iron oxide. Examples of iron oxide
providing compounds include goethite, hematite, magnetite,
maghemite, lepidocricite and mixtures of any two or more
thereof.
[0036] A Column 1 metal is generally added to the regenerator iron
oxide as part of the catalyst preparation. A Column 1 metal is any
metal from Column 1 of the Periodic Table, and the preferred Column
1 metal is potassium. Potassium is generally added as a potassium
compound, for example potassium carbonate, potassium hydroxide,
potassium oxide, or potassium oxalate. The amount of potassium
compound in the mixture should be such as to provide a final
catalyst having a potassium content in the range of from 5 to 40
weight percent, calculated as K.sub.2O based on the total weight of
the final catalyst. The potassium content may preferably be in the
range of from 5 to 35 weight percent, or more preferably from 10 to
30 weight percent calculated as K.sub.2O.
[0037] In addition to a Column 1 metal, additional catalyst
components are generally added that act as promoters, stabilizers
or otherwise provide beneficial qualities to the catalyst. Some
typical additional catalyst components include Column 2 metals,
cerium, molybdenum, and tungsten.
[0038] Column 2 metals, for example magnesium or calcium, or a
combination thereof may be added to the regenerator iron oxide. The
Column 2 metal component may be present in the final catalyst in an
amount in the range of from 0.1 to 15 weight percent, calculated as
the metal. The Column 2 metal content may preferably be in the
range from 0.2 to 10 weight percent or more preferably from 0.3 to
5 weight percent, calculated as the metal.
[0039] Cerium may be added in an amount such as to provide a final
catalyst having cerium content in the range of from 1 to 25 weight
percent, calculated as cerium. The cerium content may preferably be
in the range of from 2 to 20 weight percent, or more preferably
from 3 to 15 weight percent, calculated as cerium.
[0040] Molybdenum, tungsten or a combination thereof may be added
in an amount such as to provide a final catalyst having a
molybdenum or tungsten content, or a combination thereof, of from
0.1 to 15 weight percent, calculated as the metal. The molybdenum,
tungsten, or both metals may preferably be present in the final
catalyst in an amount in the range of from 0.2 to 10 weight
percent, or more preferably from 0.3 to 5 weight percent calculated
as the metal.
[0041] Other additional catalyst components that may be
incorporated in the mixture include scandium, yttrium, lanthanum,
rubidium, vanadium, chromium, cobalt, nickel, manganese, copper,
zinc, cadmium, aluminum, tin, bismuth, rare earths, and mixtures of
any two or more thereof. Among these components, preferred are
those selected from the group consisting of lanthanum, copper,
vanadium, chromium, and mixtures of any two or more thereof.
[0042] The mixture may be formed or shaped into particles. The
mixture may be formed or shaped into any form known to those
skilled in the art as being a suitable type or shape for use as a
catalyst particle. Examples of such shapes include extrudates,
pellets, tablets, spheres, pills, saddles, trilobes, and
tetralobes. One preferred method of preparing the particles is to
mix together the catalyst components with water, or a plasticizer,
or both, and form an extrudable paste from which extrudates are
formed. The extrudates may be dried.
[0043] The mixture is subsequently calcined to yield a
dehydrogenation catalyst. It is noted that in the process for
preparing a dehydrogenation catalyst beginning with the starting
regenerator iron oxide, throughout its treatment and up to the
mixing of the treated regenerator iron oxide with at least one
additional catalyst component, none of the steps include a
calcination heat treatment of the materials. It is not until the
mixture with additional catalyst component(s) is formed that a
calcination step is utilized. The omission of a calcination step
until this point in the process is a feature of the invention.
[0044] The mixture is calcined, preferably in an oxidizing
atmosphere, such as air, at a temperature in the range from about
500.degree. C. to about 1200.degree. C., preferably from about
600.degree. C. to about 1100.degree. C., and more preferably from
about 700.degree. C. to about 1050.degree. C. to form a
catalyst.
[0045] The pore volume of the catalyst described herein is at least
0.01 ml/g, and more suitably, at least 0.05 ml/g. Concerning its
upper limit, the pore volume is less than 0.5 ml/g, preferably less
than 0.25 ml/g, and more preferably less than 0.20 ml/g.
[0046] The median pore diameter of the catalyst is at least 500
.ANG., and more suitably, at least 1000 .ANG.. Concerning the upper
limit, the median pore diameter of the catalyst is less than 10,000
.ANG., and preferably less than 8,000 .ANG.. A most preferred
catalyst has a median pore diameter in the range of from 1200 .ANG.
to 6500 .ANG..
[0047] As the term is used herein, the pore volume is as measured
by mercury intrusion according to ASTM D4282-92, to an absolute
pressure of 6000 psia (4.2.times.10.sup.7 Pa), using Micrometrics
Autopore 9420 model (130.degree. contact angle, mercury with a
surface tension of 0.473 N/m). The term median pore diameter means
the pore diameter at which 50% of the mercury intrusion volume is
reached.
[0048] The surface area of the catalyst is in the range of from
0.01 to 20 m.sup.2/g. Preferably, the surface area is in the range
of from 0.1 to 10 m.sup.2/g. The crush strength of the catalyst is
suitably at least 10 N/mm, and more suitably it is in the range of
from 20 to 100N/mm.
[0049] The catalyst comprising treated regenerator iron oxide
described herein may suitably be used in the dehydrogenation of
hydrocarbons. In the dehydrogenation method, the catalyst is
contacted with a dehydrogenation feed under dehydrogenation
reaction conditions to thereby provide a dehydrogenation reaction
product. More specifically, the dehydrogenation feed is introduced
into the dehydrogenation reactor wherein it is contacted with the
dehydrogenation catalyst.
[0050] It is recognized that the dehydrogenation reactor or
dehydrogenation reactor system can include more than one
dehydrogenation reactor or reaction zone. If more than a single
dehydrogenation reactor is used, they may be operated in series or
in parallel, or they may be operated independently from each other
and under the same or different process conditions.
[0051] The dehydrogenation feed can be any suitable feed and, more
particularly, it can include any hydrocarbon that is
dehydrogenatable. Examples of dehydrogenatable hydrocarbons include
alkyl aromatics, such as alkyl substituted benzene and alkyl
substituted naphthalene, isoamylenes, which can be dehydrogenated
to isoprenes, and butenes, which can be dehydrogenated to
butadiene. The preferred dehydrogenation feed comprises an
alkylaromatic compound preferably one selected from the group of
compounds consisting of ethylbenzene, propylbenzene, butylbenzene,
hexylbenzene, methylpropylbenzene, methylethylbenzene, and
diethylbenzene.
[0052] The most preferred dehydrogenation feed is an ethylbenzene
feedstock comprising predominantly ethylbenzene. Ethylbenzene is
dehydrogenated to styrene. The dehydrogenation feed can also
include other components including diluents. It is common to use
steam as a feed diluent when ethylbenzene is a feed component to be
dehydrogenated to form styrene.
[0053] The dehydrogenation conditions can include a dehydrogenation
reactor inlet temperature in the range of from about 500.degree. C.
to about 1000.degree. C., preferably, from 525.degree. C. to
750.degree. C., and, most preferably, from 550.degree. C. to
700.degree. C. It is recognized that in the dehydrogenation of
ethylbenzene to styrene the reaction is endothermic. When such a
dehydrogenation reaction is carried out, it can be done so either
isothermally or adiabatically. In the case where the
dehydrogenation reaction is carried out adiabatically, the
temperature across the dehydrogenation catalyst bed, between the
dehydrogenation reactor inlet and the dehydrogenation reactor
outlet, can decrease by as much as 150.degree. C., but, more
typically, the temperature can decrease from 10.degree. C. to
120.degree. C.
[0054] The reaction pressure is relatively low and can range from
vacuum pressure upwardly to about 300 kPa. The absolute pressure is
typically in the range of from 10 to 300 kPa, more typically from
20 to 200 kPa, for example 50 kPa, or 120 kPa. Due to the reaction
kinetics of the dehydrogenation reaction of ethylbenzene to styrene
it is generally preferable for the reaction pressure to be as low
as is commercially feasible.
[0055] The liquid hourly space velocity (LHSV) can be in the range
of from about 0.01 hr.sup.-1 to about 10 hr.sup.-1, and preferably,
from 0.1 hr.sup.-1 to 2 hr.sup.-1. As used herein, the term "liquid
hourly space velocity" is defined as the liquid volumetric flow
rate of the dehydrogenation feed, for example, ethylbenzene,
measured at normal conditions (i.e., 0.degree. C. and 1 bar
absolute), divided by the volume of the catalyst bed, or the total
volume of catalyst beds if there are two or more catalyst beds.
[0056] When styrene is being manufactured by the dehydrogenation of
ethylbenzene, it is generally desirable to use steam as a diluent
usually in a molar ratio of steam to ethylbenzene in the range of
from 0.1 to 20. Typically, the molar ratio of steam to ethylbenzene
is in the range of from 2 to 15, and, more typically, from 4 to 12.
Steam may also be used as a diluent with other dehydrogenatable
hydrocarbons.
[0057] It is preferred for the dehydrogenation process conditions
to be such as to provide for the conversion of the dehydrogenatable
hydrocarbon compounds of the dehydrogenation feed to be in the
range of from 30 to 100 mole percent, more preferably, at least 35
mole percent, and, most preferably, at least 40 mole percent. As
used herein, the term "conversion" means the fraction, in mole %,
of a specified compound converted to another compound. For
ethylbenzene, conversion is defined as the difference between the
moles of ethylbenzene in a dehydrogenation reactor feed and the
moles of ethylbenzene in the dehydrogenation reactor effluent with
the difference being multiplied by one hundred and divided by the
moles of ethylbenzene in the dehydrogenation reactor feed.
[0058] The references herein to the activity of a catalyst are
meant to refer to the temperature parameter associated with the
particular catalyst. In the case of a styrene manufacturing
catalyst, i.e., an ethylbenzene dehydrogenation catalyst, its
temperature parameter is the temperature, in .degree. C., at which
the styrene manufacturing catalyst provides under certain defined
process conditions a specified conversion of an ethylbenzene feed.
An illustrative example of activity is the temperature at which a
conversion of 70 mole % of the ethylbenzene is achieved when
contacted with the styrene manufacturing catalyst under certain
reaction conditions. Such a temperature condition may be
represented by the symbol "T.sub.70", which means that the given
temperature provides for a conversion of 70 mole percent of the
ethylbenzene in the feed. The T.sub.70 temperature value represents
the activity of the associated catalyst. The activity of a catalyst
is inversely related to the temperature parameter with higher
activities being represented by lower temperature parameters and
lower activities being represented by higher temperature
parameters.
[0059] The reference to initial activity is the activity of the
fresh catalyst when it is first placed in use. For instance, the
initial activity of a styrene manufacturing catalyst may be
represented by its T.sub.70 value at essentially the starting time
at which it is first placed in use.
[0060] As used herein, the term "selectivity" means the fraction,
in mole %, of the converted compound that yields the desired
compound. As an example, in an ethylbenzene dehydrogenation
process, the ethylbenzene of the feedstock is considered to be the
converted compound and the desired compound is considered to be
styrene. Thus, the selectivity is the mole % of the converted
ethylbenzene that is converted into styrene.
[0061] Due to the unique catalytic properties of the treated
regenerator iron oxide based dehydrogenation catalyst, such as its
high initial activity, the operation of conventional
dehydrogenation process systems that include a dehydrogenation
reactor loaded with either a non-regenerator iron oxide based
dehydrogenation catalyst or a conventional regenerator iron oxide
based dehydrogenation catalyst can be improved by removing from the
dehydrogenation reactor the catalyst load and replacing it with a
treated regenerator iron oxide based dehydrogenation catalyst as is
described in detail herein. The thus-loaded or reloaded
dehydrogenation reactor is a modified dehydrogenation system
including a dehydrogenation reactor loaded with a treated
regenerator iron oxide based dehydrogenation catalyst having the
low chloride concentration as noted herein.
[0062] As it is referred to in this specification, the conventional
regenerator iron oxide based dehydrogenation catalyst is a catalyst
composition that is based on an iron oxide component in that its
iron oxide component comprises predominantly regenerator iron oxide
having a chloride content greater than 500 ppmw.
[0063] The dehydrogenation system that includes a reactor loaded
with a treated regenerator iron oxide based dehydrogenation
catalyst is operated by contacting a dehydrogenation feed under
dehydrogenation reaction conditions to thereby provide a
dehydrogenation reaction product. More specifically, the
dehydrogenation feed is introduced into the dehydrogenation reactor
containing the treated regenerator iron oxide based dehydrogenation
catalyst wherein it is contacted with the catalyst.
[0064] The following Examples are presented to illustrate the
invention, but they should not be construed as limiting the scope
of the invention.
EXAMPLE I
[0065] This Example presents information on the properties of the
regenerator iron oxides A, B, and C used in the preparation of
Catalysts 1, 2 and 3 and descriptions on how the Catalysts were
prepared.
[0066] Table I presents certain of the chemical and physical
properties of iron oxides A, B and C. The iron oxides A and B are
typical iron oxides prepared by the heat decomposition of iron
chloride (regenerator iron oxide) and which were not subjected to
additional treating, calcination or other chloride reduction
treatments. Iron oxide C was obtained from the same supplier of the
iron oxides A and B but was further treated by water washing in
accordance with the invention to further reduce the chloride
content.
TABLE-US-00001 TABLE 1 Selected Chemical and Physical Properties of
Iron Oxides A, B, and C Untreated Treated Iron Iron Property Iron
Oxide A Iron Oxide B Oxide C Oxide C Cl (wt. %) 0.098 0.111 0.088
0.029 SiO.sub.2 (wt. %) 0.009 0.010 0.008 0.011 Na.sub.2O (wt. %)
0.010 0.011 0.007 0.003 CaO (wt. %) 0.013 0.015 0.013 0.004 MnO
(wt. %) 0.264 0.269 0.266 0.258 Cr (wt. %) 0.018 0.016 0.015 0.016
Cu (wt. %) 0.010 0.010 0.006 0.006 Al.sub.2O.sub.3 (wt. %) 0.058
0.065 0.0065 0.066 P (wt. %) 0.009 0.010 0.009 0.009 MgO (wt. %)
0.007 0.009 0.006 0.003 TiO.sub.2 (wt. %) 0.009 0.012 0.007 0.010
Ni (wt. %) 0.017 0.021 0.015 0.014 Apparent 0.58 0.57 0.52 0.59
density BET 3.47 3.51 3.41 3.76
[0067] As can be seen from the table, the water washing removes
other impurities in addition to chlorides. Removing these
impurities is an additional advantage of this invention. Also, the
table demonstrates that the treated iron oxide does not have a
smaller surface area than the untreated iron oxide. In fact, in
this example, the treated iron oxide has a larger surface area than
the untreated iron oxide.
[0068] Catalyst 1 was prepared by first forming a paste by mixing
untreated iron oxide A, yellow iron oxide (Bayer, type 920Z),
potassium carbonate, cerium carbonate, molybdenum trioxide, calcium
carbonate, and water (about 9 wt. %, relative to the weight of the
dry mixture). The paste was extruded to form 3 mm diameter
cylinders cut into 6 mm length extrudate particles. The pellets
were dried in air at 170.degree. C. for 15 minutes and subsequently
calcined in air at 825.degree. C. for 1 hour. After calcination,
the composition of the catalyst was, on a per mole of iron oxide
(as Fe.sub.2O.sub.3) basis, 0.516 mole potassium, 0.066 mole
cerium, 0.022 mole molybdenum, and 0.027 mole calcium. The quantity
of yellow iron oxide was sufficient to provide 8.8 mole %, as
Fe.sub.2O.sub.3, relative to the total moles of iron oxide, as
Fe.sub.2O.sub.3, in the catalyst.
[0069] Catalyst 2 was prepared in the same manner as described
above for Catalyst 1; except that, the untreated iron oxide B was
used in place of untreated iron oxide A.
[0070] Catalyst 3 was prepared in the same manner as described
above for Catalyst 1; except that, treated iron oxide C was used in
place of untreated iron oxide A.
EXAMPLE II
[0071] This Example describes the procedure by which the Catalysts
1, 2 and 3 of Example I were tested, and it presents the results of
such testing.
[0072] A 100 ml sample of each of the Catalysts described in
Example I was used for the preparation of styrene from ethylbenzene
under isothermal testing conditions in a reactor designed for
continuous operation. In each test, the conditions were as follows:
absolute pressure of 76 kPa, steam-to-ethylbenzene molar ratio of
10, liquid hourly space velocity of 0.65 liter/liter/hr. In each
test, the reactor temperature was maintained at 600.degree. C. for
a period of 7 to 10 days. The reactor temperature was thereafter
adjusted until a 70% mole conversion of the ethylbenzene was
achieved.
[0073] Presented in FIG. 1 and FIG. 2 are results of the
above-described testing. FIG. 1 shows the calculated catalyst
activity (T.sub.70) plotted as a function of time (days) in use.
FIG. 2 shows the actual ethylbenzene conversion plotted as a
function of time (days). Catalyst 3 achieves a high conversion
shortly after startup, but Catalyst 1 and Catalyst 2 require more
than one week to achieve stable performance at the target
conversion. As may further be observed from the plots, Catalysts 1
and 2 exhibit significantly lower initial activities than Catalyst
3. Also, Catalyst 3 exhibited a relatively stable activity in that
the activity of the catalyst did not significantly change from its
initial activity with time in use. However, Catalysts 1 and 2
demonstrated an increasing activity with time in use from their
initial activity. The rate of increase in the activity of the
Catalysts 1 and 2 tended to decline during an initial break-in
period to a point in time at which their activity stabilized at an
activity level comparable to that of Catalyst 3. Due to the higher
initial and relatively stable activity of Catalyst 3, its use in a
dehydrogenation process can provide significant operational and
economic benefits by eliminating the need for a break-in period.
Catalysts 1, 2 and 3 respectively exhibited selectivities,
S.sub.70, of 95.5%, 95.1% and 96.0%.
[0074] Reasonable variations, modifications and adaptations of the
invention may be made within the scope of the described disclosure
and appended claims without departing from the spirit and scope of
the invention.
* * * * *